Exponential dichotomies of evolution operators in Banach spaces

This paper considers three dichotomy concepts (exponential dichotomy, uniform exponential dichotomy and strong exponential dichotomy) in the general context of non-invertible evolution operators in Banach spaces. Connections between these concepts are illustrated. Using the notion of Green function, we give necessary conditions and sufficient ones for strong exponential dichotomy. Some illustrative examples are presented to prove that the converse of some implication type theorems are not valid

The Effect of an Enhanced Recovery Protocol on Pediatric Colorectal Surgical Patient Outcomes at a Single Institution

Introduction Enhanced recovery protocols (ERP) have been associated with fewer postoperative complications in adult colorectal surgery patients, but there is a paucity of data on pediatric patients. Our aim is to describe the effect of an ERP, compared to conventional care, on pediatric colorectal surgical complications. Materials and Methods We performed a single institution, retrospective cohort study (2014-2020) on pediatric (≤18 years old) colorectal surgery patients pre- and post-implementation of an ERP. Bivariate analysis and logistic regression were used to assess the effect of an ERP on return visits to the emergency room, reoperation, and readmission within 30-days. Results There were 194 patients included in this study, with 54 in the control cohort and 140 in the ERP cohort. There was no significant difference in the age, BMI, primary diagnosis, or use of laparoscopic technique between the cohorts. The ERP cohort had a significantly shorter foley duration, postoperative stay, and had nerve blocks performed. After controlling for pertinent covariates, the ERP cohort experienced higher odds of reoperation within 30 days (OR 5.83, P = .04). There was no significant difference in the other outcomes analyzed. Conclusion In this study, there was no difference in the odds of overall complications, readmission or return to the ER within 30-days of surgery. However, although infrequent, there were higher odds of returns to the OR within 30 days. Future studies are needed to analyze how adherence to individual components may influence patient outcomes to ensure patient safety during ERP implementation

Sap Transporter Mediated Import and Subsequent Degradation of Antimicrobial Peptides in Haemophilus

Antimicrobial peptides (AMPs) contribute to host innate immune defense and are a critical component to control bacterial infection. Nontypeable Haemophilus influenzae (NTHI) is a commensal inhabitant of the human nasopharyngeal mucosa, yet is commonly associated with opportunistic infections of the upper and lower respiratory tracts. An important aspect of NTHI virulence is the ability to avert bactericidal effects of host-derived antimicrobial peptides (AMPs). The Sap (sensitivity to antimicrobial peptides) ABC transporter equips NTHI to resist AMPs, although the mechanism of this resistance has remained undefined. We previously determined that the periplasmic binding protein SapA bound AMPs and was required for NTHI virulence in vivo. We now demonstrate, by antibody-mediated neutralization of AMP in vivo, that SapA functions to directly counter AMP lethality during NTHI infection. We hypothesized that SapA would deliver AMPs to the Sap inner membrane complex for transport into the bacterial cytoplasm. We observed that AMPs localize to the bacterial cytoplasm of the parental NTHI strain and were susceptible to cytoplasmic peptidase activity. In striking contrast, AMPs accumulated in the periplasm of bacteria lacking a functional Sap permease complex. These data support a mechanism of Sap mediated import of AMPs, a novel strategy to reduce periplasmic and inner membrane accumulation of these host defense peptides